This invention relates generally to the detection of electrical signals and more particularly to an improved apparatus and method for detecting the presence of received signals in a noisy environment.
As is known in the art, it is often necessary to detect the presence of particular electrical signals being received in the presence of a noisy environment. One method for providing such detection is threshold detection, in which the magnitude of samples of a received signal are compared to a predetermined threshold level. If any such sample exceeds the threshold level, the presence of the signal is indicated. One problem with this technique however is that, in the presence of a noisy environment, the threshold level may be exceeded because of received noise and thus, the presence of the signal may be falsely indicated.
Another method known in the art for reducing the occurrence of such false signal indications is to filter the received signal by averaging a plurality of successive samples of the received signal and comparing the averaged value to the threshold level to provide the signal presence indication. The averaged sample value is ideally unaffected by white noise since the average value of such noise approaches zero. However, a drawback of this technique is that, due to the practical limitation of the number of samples used to compute the averaged sample value, some error will occur as a result of received noise. In other words, in applications where the signal to noise ratio of the received signal is below a certain value, the rate of false signal indications may be unacceptable.